Centrifuge comprising a slowly rotating drum in a casing revolving at high speed

ABSTRACT

A centrifuge having a slowly rotating drum within a case with the latter revolving at high speed and the case has cells and outflow passages at the rear side of the centrifuge and at separating cells thereof.

United States Patent Schulz 1 51 Aug. 15, 1972 [54] CENTRIFUGE COMPRISING A SLOWLY ROTATING DRUM IN A CASING REVOLVING AT HIGH SPEED [72] Inventor: Herbert Schulz, Fritz-Reuter-Allee 29, Berlin 17, Germany [22] Filed: July 30, 1970 [21] App]. No.1 59,509

52 us. Cl .Q .233/32, 233/46 511 int. Cl. ..,....B04b 1/00 [58 1 Field 6: Search .233/7, 20 R, 46, 27, 28, 29,

[56] References Cited UNlTED STATES PATENTS 2,073,496 3/1937 Schulz ..'.....'.....233/28 2,270,173 1/1942 Schulz .233/28 3,389,855 6/1968 Muller ..233/2 FOREIGN PATENTS OR APPLICATIONS 1,120,381 12/1961 Germany ..233/28 7 l 8,646 12/1954 England ..233/28 21,084 4/1961 Germany ..233/28 1,102,050 3/1961 Germany ..233/28 1,056,542 4/1959 Germany ..233/25 9/1934 Germany ..233/21 Primary Examiner-Jordan Franklin Assistant ExaminerGeorge H. Krizmanich Attorney-Watson, Cole, Grindle & Watson 5 7] ABSTRACT A centrifuge having a slowly rotating drum within a case with the latter revolving at high speed and the case has cells and outflow passages at the rear side of the centrifuge and at separating cells thereof.

12 Claims, 9 Drawing Figures PATENTEU I972 3.684.162

SHEEI 1 OF 5 Fig.1-

- lnvenlor:

Herbert 303022 By M j m Wm PATENTEDAUG 15 1912 SHEET 5 OF 5 m van/0r: f/wlmf 502L022 CENTRIFUGE COMPRISING A SLOWLY ROTATING DRUM IN A CASING REVOLVING AT HIGH SPEED In the case of centrifuges comprising a slowly rotating drum within a casing revolving at high speed and over-pressure in the separating spaces, it is impossible with high performance and conventional acceleration figures and by means of three consecutive short separating operations to obtain both pulverulent deposited substances and trace-free" outflow at the same time. This is because liquid, containing solid particles, reaches the outflow while avoiding all separation action through small passages in the cell walls on the scraping surfaces which are needed outside the water ring for drying the solids. These transverse flows tear solid particles already deposited off the scraping surfaces and carrying them into the outflow, since they cannot be deposited by sinking speed against centrifugal force in fractions of seconds. To keep these losses small, the passage cross-sections should be small and the reflux outside the water ring is slow and prevents an extraordinary dryness of the solid substance.

As a consequence of the oblique position of the cell walls relative to the axis of the casing at the level of the liquid, the scraping tips are dipped first into the ring of liquid during the second rotary displacement of the drums, and as a result of the required seal of the scraping, hollow spaces are formed on the rear sides of the scrapers which fill suddenly with liquid only after immersion of the passages in the cell walls. These surges occur 80 to 120 times per minute, cause the pressure in the liquid ring to rise and drop and thereby disturb all separating operations.

By employing the tooth gaps as nozzles according to DBP 1,193,434, the jet of mixture is unfavorably injected parallel to the annular wall.

To prevent stirring up the deposited solids on the annular wall by this direction of the jet, the speed and power of injection must be lower during the second separating operation than during the first. As a result of unavoidable clearance between the scraper and scraped surface, a small proportion of solid particles reaches the outflow, because one sealing surface is insufficient for three separating operations, so that the outflow still contains 0.02 to 0.04 percent of solid particles.

To increase the number of separating actions in the ring of liquid by raising the number of cells at the periphery of the drum, until the outflow is trace-free is impossible with the known application of the tooth gaps as nozzles, because the tooth gaps and the lower cells can be employed once only in the separating space owing to rotation of the drum.

A substantial improvement which largely eliminates the disadvantages of the tooth gaps employed as nozzles, unimpeded transverse flows through passages and up to the outflow, disturbance by surges in the separating actions, and no possibility of incorporating more separating actions than known, is accomplished according to the invention by virtue of the fact that by closure of the passages in the cell walls the entire centrifuged material is guided in the nozzles of the successively positioned cells up to the outlet, and the contrary to known procedure, it is possible to perform three consecutive separating operations in four to six or more cell spaces, so that the required number of separating operations for trace-free outflow can be correlated to any mixture.

According to the invention, the liquid flows through.

a depression in the scraping wall at the height of the liquid level to the rear side of the cells walls upon immersion of the same, and prevents the pressures from rising and dropping during all separations. I

By incorporation of solid ledges on the scraping surface in the ring of liquid, the cross-sections of the passages in the cell walls are filled in the separating space, so that transverse flows to the outlet are impossible, and each consecutively arranged separating space is closed ofi except for the injection and outflow openings through which the entire centrifuged material flows, whereas the known reflux of the liquid occurs through the open passages into the subsequent cells for the drying of the solid on the way to the discharge. As a result of these ledges, the passage cross-sections can be increased optionally, and the return flow of the liquid caused by centrifugal force along the drying path occurs more quickly so that a higher output or drier pulverulent solids are obtained by a higher speed of revolution of the drum.

The spaces between the cell walls are divided into upper and lower separating spaces by partitions and the outflow of the entire centrifuged material from the upper into the lower cells occurs at each rear side through narrow slots. From the lower spaces, the entire mixture is conveyed by means of pipes in the rear sides and appropriately through the antechambers into the nozzles of the following cells, so that six cells which are immersed in the ring of liquid are traversed consecutively up to the outflow pipe. For incorporation of these pipes or passages, the partitions of the antechambers are appropriately staggered relative to the cell walls.

In the consecutively positioned traversed six separating spaces occur the known separating actions in vertically and laterally adjacent cells in the same manner by injection and by restriction of six outflows, so that corresponding to the six separating spaces traversed, six stepped consecutive overpressures are engendered, which have the effect that in six cells, the liquid already spreads out at a small distance from the six inflow openings over the cross-sections of the six cells for reduction of the flow velocity so that the slower flow does not entrain the particles retained by centrifugal force on the scraping and the scrapers thus carry the solid deposited to the discharge.

Solid particles which are forced through the scraper gap by overpressure during the first and second separating actions and by centrifugal force through return passages outside the ring of water into subsequent cells, thus undergo several additional separating operations up to the outflow pipe. Owing to application of nozzles in three or six upper separating spaces, the injection of the centrifuged material occurs with identicaldirection and speed, whereas according to the lower acceleration figure, the injection into the three lower cells occurs with lower speed and greater cross-section to obtain identical outputs. By increasing the number of cells and arranging the cells beside each other, the injection into six upper cells is performed consecutively through nozzles, and the outflow from each cell occurs into the antechamber of the next nozzle, to obtain a simpler centrifuge with higher acceleration figures in all separating spaces.

The surges are eliminated from the separating actions by uniform filling of the cavities behind the cell walls upon immersion into the ring of liquid.

As a result of the further ducting of the mixture through the antechambers, the passages at the periphery of the drum and the gap between the denticulated head and the stationary middle wall are sealed off by laterally displaceable bars, so that parti cles of the mixture cannot pass from the first to the last separating action.

The inflow of mixture into the antechambers through open annular slots occurs laterally to the axis of the drum. So that splashes of mixture cannot reach subsequent antechamber owing to the curvature, these slots are screened off at the outflow connector by circle segments.

These six consecutive separating actions occur simultaneously at four points in the centrifuge.

Instead of being injected into the spaces between the drums, precipitants are injected into the antechambers of the nozzles for the third separating actions, so that they have more time during four separating actions, in-

' stead of two as known, to effect sudden fixing by pressure and turbulence of colorants among others, in order to extract these together with the solids.

An increase in the number of cells increases the number of cells in the ring of water, and the number of separating actions is increased accordingly.

By closure of the individual separating .spaces and sealing of the antechambers against penetration of air, solid particles are separated from air and gaseous mixture. If the liquid is omitted, a multiple of the customary acceleration factor is produced, and the solid particles are entrained continuously from a gaseous mixture.

So that the gaseous mixture may be forced to undergo all the separating actions, the outflow passages in the antechambers are closed off by leaf springs which are opened only by overpressures in the cells.

The centrifuged material is injected in known manner by means of nozzles against the outer wall of the upper cells in approximately radial direction for the first separating action. By construction of the outflow at the rear side of the cells through a gap between a guiding plate and the wall of the drum, the inflowing mixture generates an over-pressure in the cell space which, according to the inflow velocity out of the nozzles suddenly reduces the cell cross-section and thereby reduces the scavenging force of the flow so far the centrifgual force holds the solids fast on' the scraping surface, Through the gap at the rear side of the cell, which acts as a nozzle, the denuded centrifuged material flows quickly into the lower cell for the second separating action, and the narrow outflow passage at the rear side of the cell generates the overpressure in the cell space which suddenly reduces the inflow velocity according to the cell cross-section, so that the flow becomes so small that the solids deposited are held on the scraping surface by centrifugal force. During the lifting of the solids off the scraping surface for entrainment to the point of discharge, the particles dislodged by turbulence are injected together with the denuded centrifuged material into the lower second separating space, and the mixture further denuded passes through the narrow outflow passage at the rear side of the cell into the antechamber of the nozzle for the subsequent cell, which projects the centrifuged material against the outer side of this cell space in the same way, direction and action for the third separating operation. Constructed outflows which generate over-pressure in the separating spaces between two cell walls, four six or eight and more separating actions are produced con secutively by optional spacing apart of the known narrow outflow opening from the axis of the drum, with stepped overpressures, so that the required number of separating actions may be correlated to the finest separable mixtures to obtain a trace-free outflow.

The liquid from the tooth gaps, upon issuing from the ring of liquid, flows through passages at the periphery of the drum into the upper cells and, with their liquid, flows back through the passages in the cell walls which are open at these points, into the first separating spaces. Entrained solid particles are exposed to another five separating operations up to the outlet, with the entire centrifuged material. In the rotation of the drum, the denticlated heads and passages are appropriately wrought as scrapers and are sealed off in the ring of liquid by laterally displaceable ledges or bars pressed on by springs, so that no gap is formed by wear upon resetting the drums. The return flow of the cell liquid occurs initiallyv through the passages at the rear side into the following nozzle. The greater residual portion is forced into the first separating action in fractions of seconds by means of centrifugal force and drum rotation through the passages at the scraping wall. By closure of the passages by means of bars, in the separating space, their cross-sections are of optional size, the return flow is faster, the expressing period of the solids on the cell walls is thus longer and they are extracted continuously in pulverulent form. A very long period of operation is obtained by means of appropriately exchangeable hardened steel plate or of hard platings, for example, hard chromium plating.

The invention consists in centrifuge comprising a drum rotating within a case revolving at high speed, whereof the axis intersects the axis of the drum, with cells arranged on the periphery of the drum, in which cells prevails an overpressure and whose discharge openings are covered by fixed walls, characterized by constriction of the outflow passages at the rear side of the consecutively situation traversed separating cells whereof the number is variable and which in these cells dam up the rapidly inflowing mixture so that by virtue of stepped over-pressures in an traversed cell the liquid spreads over these cell cross-sections.

Further details of the invention emerge from the examples of embodiment illustrated in the drawings. In these:

FIG. 1 is a longitudinal section through the centrifuge corresponding to the sectioning II-II in FIG. 2,

FIG. 2 is a longitudinal section at right angles to the sectioning line II in FIG. 1,

FIG. 3 is a section through the drum corresponding to line III-III IN FIG. 1,

FIG. 4 is a partial section through the inner drum with two superposed separating spaces to enlarged scale,

FIG. 5 is a partial section at right angles to the partial section according to FIG. 4,

FIG. 6 is a partial section at right angles to the partial section according to FIG. 5 for reproduction of the flows, i

FIG. 7 is a partial section through the inner drum with a separating space to enlarged scale,

FIG. 8 is a partial section at right angles to the partial section according to FIG. 7,

FIG. 9 is a partial section at right angles to the partial section according to FIG. 8, for reproduction of the flows.

As apparent from FIGS. 1 and 2, the outer drum casing 1 is rotatably jounalled in bearing 2 and 3 and is driven at high speed by means of a belt pulley 4.

Through a pivot bearing of the drum' case 1 passes a' shaft 5 from which drive is transmitted by means of bevel gears 6 and 8 and from a belt pulley 7 to the' drums 11 to turn the latter slowly around the shaft 9 at right angles to the drum case 1. Both drums 11 are firmly joined around their axis, on their outer peripheries have cells 18 and 22 whereof the open sides cover scraped walls of the drum case 1 which are interrupted at the ejection openings 12 (FIG. 1) for discharge of the solids. The inflow of the centrifuged material occurs in the direction of the arrow 13 (FIGS. 1 and 2), and, owing to partitions 14, passes simultaneously at four points in the centrifuge through outflow stubs 15 (FIGS. 1-9) in consequence of centrifugal force through antechambers 16 to reach the cells 18 through nozzles 17 for the initial separation.

The mixture diluted during separating action I in the first cells 18 (FIG. 6 and FIG. 4) flows over the partition 20 through the opening 21 for further dilution into the lower cell space 22 for separating action 11, appropriately passes through a pipe of passage 23 (FIG. 4 6 on the rear side of the cell into the antechamber 16 of the cell 18 behind it in the direction of rotation, is injected by its nozzle 17 for further purification into the second cell 18 for separating action III, again passes through opening 21 for separation in the lower cell space 22 for separating action IV, flows through passage 23 into the next antechamber 16, is injected by its nozzle 17 into the third cell 18 for repeated separation in separating action V, passes through opening 21 for final purification into the third cell space 22 for separating action VI and then through opening 42 (FIG. 6) to the outflow pipe 25, whereas the solids deposited are carried by the rotation of the drum from the cell walls 32 to the discharge opening 12 (FIG. 2).

In FIG. 7 9, all the partitions are arranged side by side, and the centrifuged material passes from the passage 23 at the rear side of the cell through antechamber 16 of the next cell 18 being injected through its nozzle 17 and retained in this cell for separating action II. Identical actions occur in all four following cells for separating action III VI, up to the known outflow opening 24. The distance of the outflow openings 24, 24a, from the plane through the axis 9 of the drum is appropriately variable. Outflow cells 22a which are flatter than the bars 30 to close these off in the separating space, lead to the outflow 24, 25. These bars 30 fastened on the scraping walls 10 serve the purpose of closing off the passages 29 of the cell walls 32 in the area of .the ring of liquid. Upon emergence of the cells from the ring of liquid, the return flow of the liquid occurs through passages 29 in the cell walls 32. In the ring of liquid, the passages 29 are closed off by the bars 30 on the scraping wall 10 so that the entire centrifuged material flows off only through the passages 23. Upon immersion of the cell wall 32 into the ring of liquid, the liquid flows through the depression 40 in the scraping wall 10 from the front side to the rear side without impediment, under avoidance of cavities. Upon emerging from the ring of water, the water from each gap between teeth flows owing to drum rotation through passages 31 at the periphery and back into the cells 18 further with the liquid out of the cell. The denticulated head surfaces and passages 31 are sealed off laterally in the separating space by means of bars 41 and 42 displaceable in the axis of the drum, so that no solid particles penetrate into the following separating volumes from the first to the sixth separating actions. For easier assembly and for taking up of wear, springs 43 press the bar 24 onto the toothed heads. They are held fast in the ring of water by means of wedges 44. The passages 41 toothed heads being wrought as scrapers, solids are carried to the discharge opening. The passages 31 situated on the periphery of the drum establish a connection to the cells passing out of liquid and passing into the ring of liquid. The metal bars 26 on the partitions 20 laterally retain the solids and deflect the flow off the scraping walls 10. The partitions 27 (FIGS. 5,6,7,9) of the antechambers 16 are arranged relative to the cell walls 32. The cell walls 32 as well as the scraping walls 10 are protected by replaceable hardened steel plates 45 and 46 (FIGS. 7-9), to insure great durability.

The section according to FIGS. 4 to 6 which show enlarged illustrations of parts of the cells in FIG. 3, disclose that the centrifuged material enters the cell 18 through the nozzle 17, strikes the wall of the drum, is deflected without turbulence by the obliquity 19 to the lower part of the cell against centrifugal force, and being ducted over the unperforated partition 20 issues through the opening 21, so that a circulating motion occurs in the cell 18.

The outflow opening 21 before the rearward cell wall is constructed to the extent that an overpressure is engendered in the cell 18,'which causes the water to spread out and thus reduces the flow velocity abruptly.

After leading the cell space 18, the greatly diluted centrifugal material is injected into the lower separating space 22 through the narrow slot 21 and which acts as a nozzle with the bar 28. The position and narrowness of the outflow opening 23 deflects and retains the mixture jet so that an overpressure is engendered for spreading out the liquid, the flow velocity being reduced abruptly thereby. The same actions occur twice more in the same form up to the narrow outlet 24, so that the entire centrifuged material is separated in six consecutive separating actions to obtain a pure outflow.

The depression 40 in the scraping wall 10 equalizes the liquid level in front of and behind the cell walls 32 upon immersion into the ring of liquid, An increase and decrease of the pressures in all separating cells which would be caused by the slow drum rotation, is prevented thereby.

The number of cells on the periphery of the drum being increased, more cells are immersed in the ring of water, and more than six separating actions are accordingly produced consecutively, a pure outflow being obtained from the most difficult mixtures thanks to their number.

The resistances during through flow of many consecutive separating spaces cause a rise in the water level in the first separating action and thus shorten the drying path of the solids. For equalization by faster return flow of the liquid, thepassage cross-section 29 in the cell walls are made correlatively greater, because they are closed off by bars 30 in the separating space, so that their size has no effect on the separation.

Owing to displacement of the partitions 27 relative to the cell walls 32 the passages 23 are situated in the rear walls of the cells, and owing to lateral arrangement of the outflow stub 15, the separating actions are evenly divided on both sides of the drum axis 9, so that six cells are positioned within the ring of water.

The inflow of liquid centrifuged material into the ante-chambers 16 occurs through annular slots 33, which are closed off in the separating space by circle segments 34 at the outflow stub 15, so that no splashes of mixture caused by angular inflows can pass through the following prechambers into the third separating actions. In the case of gaseous mixture, the annular slots 33 are closed off throughout the periphery by circle segments 34 completed to form a cylinder (FIG. 6). By displacing the outflow opening 24 to 24a towards the plane of the drum axis, the number of separating actions is reduced and the drying path is lengthened, so that an optional degree of dryness of the solids and a pure outflow can be established for any mixture.

For infeed of precipitants, the case 1 has a trough 35 from which two passages 36 in each half of the middle partition 37 up to the middle of the drum lead into two passages 38 (FIG. 4 and 7 )which extend parallel to the axis of the drum and lead into the four prechambers of the 'third separating action. The precipitants are injected by centrifugal force into these prechambers so that pressure and flow turbulence may cause abrupt fixing of colorants and analogous suspended substances, separation of these from the third to sixth separations and issuing of these together with the solids.

The period of separation of a centrifuged material, measured between each nozzle opening and scraping wall amounts to between one-fiftieth to one-one hundred fiftieth of a second for solid discharge with tracefree outflow, usual acceleration factor and corresponding to the proportion of solids, so that small centrifgues already enjoy a high performance. High injection velocities cause turbulence with abrupt temperature rise, intensifies the susceptibility to flocculation of the finest suspensions, and the addition of small quantities of precipitants in the application of this centrifuge in hydraulic engineering offers great economic advantages. Upon centrifuging a gaseous mixture, small gas volumes corresponding to cell capacity are carried to the discharge opening 12 by over pressure, in step with the slow drum rotation. Consequently, it is possible to omit the passages 29 and 31 from the cell walls and from the periphery of the drum, and each separating space is wholly closed off except for the inflow and outflow openings. For mixtures, the passages 23 in the prechambers 16 are appropriately closed off by leaf springs 39 (FIG. 7) which are forced shut by overpressures in the prechambers 16 of the 1st separating actions in the passages 23, and are opened by overpressure by mixture flowing out of the following separating actions into the prechambers 16, so that no gaseous mixture can pass in the direction of rotation to the discharge opening 12 through the nozzles. Owing to complete screening of the annular slots 33 by means of cylinders 34, gaseous mixtures containing solids must flow through six separating spaces under over pressure, are separated abruptly six times, the solid particles are held fast on the scraping wall by the high centrifugal force, and the scrapers carry these to the discharge openings.

Owing to elimination of the strains caused by hydraulic load, centrifugal forces amounting to a multiple of the known acceleration factor 2,500 are reached with this centrifuge thanks to its form. In the case of gas, it is appropriately operated within a sealed container.

With respect to the embodiment of FIGS. 4, 5 and 6. operation of the device is as follows. The entire centrifuge is rotated about the axis XX by the pulley 4 at centrifuging speed to normally establish an annular ring of material undergoing centrifugation. The inner surface of the ring of material is designated in FIG. 6 by the reference numeral 100. Simultaneously with the rotation of theentire apparatus about axis XX, the drums! l are rotated about the axis of shaft 9 at a much slower revolutionary speed. It is to be understood in this respect that the drums 11 rotate with the hollow casing 1 of the centrifuge about the axis XX and simultaneously the drums ll rotate relative to the hollow casing 1 about the axis of shaft 9.

Material to be centrifuged enters the device through ducts 15, which extend through an annular-wall 34 disposed to normally close the material receiving input openings 33. (It is to be understood that there are two ducts 15 for each drum; however, only one is specifically illustrated in view of the fact that all ducts 15 operate in the same manner.) In FIG. 6, duct 15 is in fluid communication, through opening 33a with a cell disposed adjacent thereto. This cell is designated as in FIGS. 4-6. Material to be centrifuged thus passes through duct 15, through opening 33a and into antechamber 16a from whence it is discharged through nozzle 17a into cell 18a. The material circulates through cell 18a, crosses deflector 20a, passes downwardly through opening 210 between deflector 20a and bar 28a and circulates through space 22a. A passageway 23a is provided in the wall of space 22a for communicating the latter with the antechamber 16b of a cell 18b which is disposed adjacent cell 18a in a direction opposite to the direction of rotation of drum 11. Cell 18b is identical in operation and structure with cell 18a and after the material traverses cell 18b, it is discharged through opening 23b into another identical cell 18c.

Viewing FIG. 6 it can be seen that the space 22c of cell 18c is in fluid communication with outlet duct 24 and accordingly fluid from which particles have been removed is free to flow outwardly through duct 24 and into the outflow pipe 25. Thus, the material entering through duct 15 traverses cells 18a, 18b, and 18c, in a direction generally opposite to the rotation of drum 1 1, whereby a series of separate centrifuging operations are accomplished. Manifestly, it is to be understood that, in view of the fact that drum 11 rotates about the axis of shaft 9, new cells continually move into proximity relative to duct 15 and cells previously in proximity therewith move on toward the ejection openings 12 where solids may be discharged.

The operation of the embodiment illustrated in FIGS. 7, 8 and 9 is quite similar to that described above except that in this instance there are no lower centrifuging areas such as were provided by the spaces 22 in FIGS. 443. In this embodiment the fluid is discharged through nozzle 17a and is circulated in cell 18a. The connecting passage 23a directly interconnects cell 18a with antechamber 16b of cell 18b. After leaving cell 18b the material traverses cells 18c, 18d,- 18e, and 18f in seriatim and leaves the apparatus through discharge duct 24. It can be seen from FIG. 9 that by placing the discharge duct at the locations identified by the reference numeral 24a, fewer centrifuging stages can be placed into operation.

I claim:

I 1. A centrifuge for heavy light and heavy fractions of a fluid material comprising:

a hollow casing;

means for rotating said casing about a first axis at a centrifuging speed sufficient to normally establish an annular ring of said fluid material to be centrifuged therein during centrifuging operations of the centrifuge;

a drum mounted for rotation within said casing about a second axis which intersects the first axis, said drum being disposed such that its periphery will be partially submerged in said ring of material during normal centrifuging operations; and

means for rotating the drum about said second axis,

said drum including means defining a plurality of centrifuging cells arranged in a series thereof extending circumferentially of the drum,

each cell including means defining a heavy material discharge port, means defining a light material, discharge port and means defining a material receiving input opening,

said casing including fixed wall means disposed adjacent the drum for normally blocking said discharge ports and said input opening during said rotation of the drum, said drum including means defining respective fluid conduits intercommunicating each cell with the means defining the input opening of the cell disposed adjacent thereto in a direction opposite to the direction of rotation of the drum, whereby normal centrifuging operations flow of fluid between cells is permitted in a direction generally opposite to the direction of rotation of the drum,

there being a light material discharge duct, a heavy material discharge duct and an input material duct extending through the wall means and opening toward the drum, said ducts being disposed for communicating periodically with the discharge ports and input openings during said rotation of the drum,

the openings of said input material duct and said light material discharge duct being disposed to be submerged in said ring of material during normal centrifuging operations and the opening of said heavy material discharge duct being disposed to be out of contact with said ring of material during normal centrifuging operations,

said light material discharge duct being spaced circumferentially, about said second axis from said input duct in a direction opposite to the direction Ill of rotation of the drum and sufficien-tly far therefrom to preclude simul-taneous communication of said light material discharge duct and said input duct with the same cell, whereby during normal centrifuging operations fluid material undergoing centrifugation must traverse at least two of said cells prior to discharge.

2. A centrifuge as set forth in claim 1 wherein said fluid conduits include flow restriction means.

3. A centrifuge as set forth in claim 1 wherein said means defining a material receiving input opening comprises an antechamber for each cell, there being a nozzle intercommunicating each antechamber with its corresponding cell.

4. A centrifuge as set forth in claim 1 wherein each cell is separated from each adjacent cell by a respective partition extending radially of said second axis adjacent said wall means, there being a notch in each partition normally intercommunicating adjacent cells, said wall means including a circumferentially extending bar disposed for blocking said notches during rotation of each partition with the drum through the ring of material in the casing.

5. A centrifuge as set forth in claim 1 wherein each cell is separated from each adjacent cell by a respective partition extending radially of said second axis adjacent said wall means, there being a depression in said wall means disposed at the level of the inner surface of said ring of material to permit flow of material around each partition and into each cell as the same enters the ring of material during rotation of the drum.

6. A centrifuge as set forth in claim 1 wherein is provided partition means in each cell dividing the same into a radially inwardly disposedchamber and a radially outwardly disposed chamber, said partition means being disposed between said material receiving input opening and the fluid conduit of the cell and including means presenting a constricted gap for restricting the flow of fluid between said chambers.

7. A centrifuge as set forth in claim 3 wherein said antechambers are disposed adjacent said cells in a' direction axially of said second axis, the antechamber of each cell being displaced circumferentially of said second axis relative to its cell sufficiently far in the direction of rotation of the drum to position a portion thereof in axial alignment with the next adjacent cell.

8. A centrifuge as set forth in claim 20 wherein said means for rotating the drum comprises a bevel gear ex tending around the periphery of the drum, there being sealing bar means mounted in said casing adjacent said gear, in sealing, sliding contact therewith to prevent flow of fluid between the teeth of the gear.

9. A centrifuge as set forth in claim 8 wherein is provided spring means for yieldably biasing said sealing bar means into said contact with the gear.

10. A centrifuge as set forth in claim 1 wherein is provided replaceable bearing means adjacent said parts and said opening and a corresponding replaceable bearing plate on said wall means, said bearing means and said bearing plate being disposed for sliding, sealing contact during rotation of the drum relative to the casing.

1 1. A centrifuge as set forth in claim 1 wherein is included a second input duct disposed for communicating periodically with said input openings for introducing precipitants thereinto.

12. A centrifuge as set forth in claim 1 wherein is included pressure responsive leaf spring valve means normally closing said conduits for preventing fluid flow in the direction of rotation of the drum. 

1. A centrifuge for heavy light and heavy fractions of a fluid material comprising: a hollow casing; means for rotating said casing about a first axis at a centrifuging speed sufficient to normally establish an annular ring of said fluid material to be centrifuged therein during centrifuging operations of the centrifuge; a drum mounted for rotation within said casing about a second axis which intersects the first axis, said drum being disposed such that its periphery will be partially submerged in said ring of material during normal centrifuging operations; and means for rotating the drum about said second axis, said drum including means defining a plurality of centrifuging cells arranged in a series thereof extending circumferentially of the drum, each cell including means defining a heavy material discharge port, means defining a light material discharge port and means defining a material receiving input opening, said casing including fixed wall means disposed adjacent the drum for normally blocking said discharge ports and said input opening during said rotation of the drum, said drum including means defining respective fluid conduits intercommunicating each cell with the means defining the input opening of the cell disposed adjacent thereto in a direction opposite to the direction of rotation of the drum, whereby normal centrifuging operations flow of fluid between cells is permitted in a direction generally opposite to the direction of rotation of the drum, there being a light material discharge duct, a heavy material discharge duct and an input material duct extending through the wall means and opening toward the drum, said ducts being disposed for communicating periodically with the discharge ports and input openings during said rotation of the drum, the openings of said input material duct and said light material discharge duct being disposed to be submerged in said ring of material during normal centrifuging operations and the opening of said heavy material discharge duct being disposed to be out of contact with said ring of material during normal centrifuging operations, said light material discharge duct being spaced circumferentially, about said second axis from said input duct in a direction opposite to the direction of rotation of the drum and sufficiently far therefrom to preclude simul-taneous communication of said light material discharge duct and said input duct with the same cell, whereby during normal centrifuging operations fluid material undergoing centrifugation must traverse at least two of said cells prior to discharge.
 2. A centrifuge as set forth in claim 1 wherein said fluid conduits include flow restriction means.
 3. A centrifuge as set forth in claim 1 wherein said means defining a material receiving input opening comprises an antechamber for each cell, there being a nozzle intercommunicating each antechamber with its corresponding cell.
 4. A centrifuge as set forth in claim 1 wherein each cell is separated from each adjacent cell by a respective partition extending radially of said second axis adjacent said wall means, there being a notch in each partition normally intercommunicating adjacent cells, said wall means including a circumferentially extending bar disposed for blocking said notches during rotation of each partition with the drum through the ring of material in the casing.
 5. A centrifuge as set forth in claim 1 wherein each cell is separated from each adjacent cell by a respective partition extending radially of said second axis adjacent said wall means, there being a depression in said wall means disposed at the level of the inner surface of said ring of material to permit flow of material around each partition and into each cell as the same enters the ring of material during rotation of the drum.
 6. A centrifuge as set forth in claim 1 wherein is provided partition means in each cell dividing the same into a radially inwardly disposed chamber and a radially outwardly disposed chamber, said partition means being disposed between said material receiving input opening and the fluid conduit of the cell and including means presenting a constricted gap for restricting the flow of fluid between said chambers.
 7. A centrifuge as set forth in claim 3 wherein said antechambers are disposed adjacent said cells in a direction axially of said second axis, the antechamber of each cell being displaced circumferentially of said second axis relative to its cell sufficiently far in the direction of rotation of the drum to position a portion thereof in axial alignment with the next adjacent cell.
 8. A centrifuge as set forth in claim 20 wherein said means for rotating the drum comprises a bevel gear extending around the periphery of the drum, there being sealing bar means mounted in said casing adjacent said gear, in sealing, sliding contact therewith to prevent flow of fluid between the teeth of the gear.
 9. A centrifuge as set forth in claim 8 wherein is provided spring means for yieldably biasing said sealing bar means into said contact with the gear.
 10. A centrifuge as set forth in claim 1 wherein is provided replaceable bearing means adjacent said parts and said opening and a corresponding replaceable bearing plate on said wall means, said bearing means and said bearing plate being disposed for sliding, sealing contact during rotation of the drum relative to the casing.
 11. A centrifuge as set forth in claim 1 wherein is included a second input duct disposed for communicating periodically with said input openings for introducing precipitants thereinto.
 12. A centrifuge as set forth in claim 1 wherein is included pressure responsive leaf spring valve means normally closing said conduits for preventing fluid flow in the direction of rotation of the drum. 